1986 MGM 5.0 rear brakes.

[Toploader]

According to the cars owner manual, the rear brakes 'self-adjust' Is this true, or do I have to put car in reverse start and stop several times for the rear shoes to self adjust?

Thanks in advance for the education

[kishy]

The rear brakes self-adjust, by the same mechanism as when you reverse and stab the brake pedal several times

Self-adjusting refers to the fact that in the course of normal use, you will back up the car enough times to keep the brakes more or less adjusted, and not need to manually turn the adjustment screw by hand (as in non-self-adjusting vehicles). In practice, let's say you street park and always pull in nose first, and always pull into spots you can pull straight out of in parking lots, so your car doesn't see a lot of time in reverse...you might find the self-adjusting does not keep up with the wear. The self-adjuster parts also wear out and the screw can become gummed up or seized in place by corrosion, which will cause it not to self-adjust even when you do the reverse-brake trick.

[Toploader]

Well thanks for the info, I may just buy all the shit I need from Rock Auto and do a brake job. Btw, how come Rock Auto does not show a master cylinder for my '86 MGM?

[jaywish]

I would not be totally surprised if after replacing all self adjusting components and properly preparing and lubing the backing plate they still don't keep the brakes adjusted properly. Disks FTW.

[FordMan77]

They show 5 of them for the 5.0L. https://www.rockauto.com/en/catalog/...+cylinder,1836

[gadget73]

They self-adjust but only if they are somewhere in the ballpark of right to begin with. Unless the shoe makes contact it can't rock the little adjuster arm thing. Found that in my truck actually, the shoes were brand new but the adjuster was wound all the way in.

[jaywish]

I know there were times I tried mightily to get self adjusters to work well and failed. Maybe some of the aftermarket components are not up to snuff plus it is kind of a clunky design overall.

[kishy]

I've found with the wagon, which has 11" drums and got everything new (minus the backing plates), that the auto-adjust works because I can snug the brakes up by doing the reverse thing...but in the course of normal use the adjusting doesn't seem to keep up and I periodically use the reverse thing to snug them up again. Haven't been able to sort out why, and it's only a minor annoyance. But I'd definitely say the auto-adjusting is dependent on best-case scenarios in all situations.

[Toploader]

They show 5 of them for the 5.0L. https://www.rockauto.com/en/catalog/...+cylinder,1836

Jeeze I could not previously find them!........thanks.

[DerekTheGreat]

Not a fan of the reverse thing. I've found that I gotta be going straight and need a stretch of about 100ft or so in order to jam the brakes a good couple of times. Then I notice an improvement, but it's easier to adjust them manually after I've noticed a decrease in pedal feel. Five minutes with the adjuster tool and I'm set. On my GMT400 truck? Hahaha... For whatever reason, GM didn't give you an access port to the starwheel. However, if you use the parking brake regularly on that duo servo set-up, they stay adjusted. I think that's a better way for self adjust.

[Arquemann]

I think rear brake adjustment will be on my to-do list aswell when spring comes back around. My pedal goes whoosh and gets stiff after quite a bit of pedal travel.

[DerekTheGreat]

Yah, do that and you'll notice a huge improvement in pedal feel. It'll stop better too.

[jaywish]

most likely

[GM_Guy]

Just be agressive in day to day backing and stopping. Can't think of when I last adjusted rear drums on anything, I back into parking spots twice daily and I'm not gentle about it, I always check when I switch summer/winter tires and all is well. The box, and my pickup trucks.

[gadget73]

yeah you do have to actually make the brakes engage or they do nothing. Very light pedal pressure will not have the rears actually doing anything. Or just force the situation and back up a few hundred feet with some hard pedal presses. Either works.